1. Field of Invention
The present invention relates to a switching system and a method of remote switching an electrically operated device and wherein the switching system is operated by using calling signals generated by a telephone, and more particularly, but not exclusively, using sound calling signals.
2. Description of Prior Art
Various types of electrical or mechanical switching devices are remotely operated by various methods such as transmitting specific signals recognized by a receiver to connect an electrical source to a device via a switch, or else by transmitting coded signals or by generating specific sounds recognizable by a receiver system. However, most of these systems require a specific transmitter device and receiver device, and are very limited as to their operating range, that is to say, the transmitter and receiver must be located within the predetermined distance. Usually, this distance is fairly short, such as for starting ignition systems of automobiles, etc. Another disadvantage of such prior art systems is that these are quite costly because of the need of transmitters and receiver systems.
It is also known, particularly with the use of alarm systems, to protect an enclosure, to automatically generate a specific code signal on a telephone line upon detection of an alarm condition, such code signal is connected to a central control station where an alarm code can be identified by decoding the signal. These signals are usually transmitted automatically with an automatic dialing system as soon as an alarm condition is detected. A disadvantage of these systems is that they are also costly in that the subscriber must pay a service charge for the use of the telephone lines as well as the usual cost of the call if a long distance call.